The present invention relates generally to precision alignment of integrated circuit devices on a common carrier. More specifically, the present invention relates to precision alignment of integrated circuit devices corresponding to thermal ink jets on a common carrier.
Articles and publications set forth herein are presented for the information contained therein: none of the information is admitted to be statutory xe2x80x9cprior artxe2x80x9d and we reserve the right to establish prior inventorship with respect to any such information.
It is well known in the art to use an inkjet printer for applications that require a hardcopy printout on a sheet of media. For example, it is commonplace to use an inkjet printer to print on sheets of paper, transparencies, labels, and the like. In a typical inkjet printer, a carriage holds one or more ink cartridges. Each cartridge has an inkjet printhead (pen) that includes several nozzles from which ink is ejected in a direction that causes the ink to impinge on the sheet of media. Typically, the carriage must travel across the media so that each pen can reach the full area of the media. The media to be printed on is usually driven along a media axis of motion and the pen is driven along a carriage axis of motion that is perpendicular to the media axis. In color inkjet printers, two or more cartridges are needed to print color images. For instance, a color inkjet printer can have four cartridges (black, cyan, magenta, and yellow) with a pen for each color. Consequently, in a four cartridge printer, the carriage must travel the width of the media, plus the width of the four pens, plus the space between pens. Therefore, the width of the inkjet printer is determined to a large extent by the distance the carriage must travel in order to print images on the full area of the media. For example, in an inkjet plotter, the carriage may have to travel a distance greater than the width of a D-size sheet of media.
Because the carriage must travel across the media, the time it takes to print images includes the travel time for the carriage. Additionally, the mechanical components that move the carriage add to the complexity, size, and weight of the printer and are a source of noise and vibration that can be annoying to a user of the printer.
Moreover, the pens in inkjet printers require periodic alignment to ensure consistent quality in the printed image. Because the pens are mounted in separate cartridges, there is always a risk of misalignment between pens, particularly when one or more cartridges are replaced.
Prior attempts to solve the above mentioned limitations and disadvantages of multiple cartridge inkjet printers include mounting a plurality of inkjet printheads onto a wide substrate such as a multi-layer ceramic substrate or flexible substrate. Those solutions have several disadvantages.
First, expensive precision tooling is required to align the printheads to the substrate. Second, a mismatch between the coefficient of thermal expansion for the printhead and the substrate can result in thermal induced stress on the interconnect used to electrically connect the substrate to the printheads. Additionally, the mismatch can result in misalignment between the substrate and the printheads. Third, the interconnect, the materials used for the substrate, and adhesives used to attach the printheads to the substrate are subject to failures due to the corrosive effects of the ink used in inkjet printers. Forth, the inkjet pens are sensitive to temperature variations caused by waste heat from the printheads. The substrate must have a high thermal conductivity so that the waste heat can be dissipated. If the substrate has a low thermal conductivity, then the waste heat can raise the temperature of the pens resulting in an increase in the pens drop volume. Subsequently, a temperature differential exists among the printheads so that the drop volumes of the printheads can vary depending on their location on the substrate. Ideally, the thermal conductivity of the substrate and the printheads would be identical so that there is no temperature differential between the printheads resulting in consistent drop volumes among the printheads.
One manner in which multiple printhead alignment can be achieved is described in an application filed by the assignee of the present application. According to this technique, a common carrier substrate is formed having one or more precisely formed pockets. The sides of each pocket are formed to have a side profile that is a near perfect compliment of the side profile of each of a set of fully integrated chips. Due to the complementary side profiles, the chip can be positioned in near perfect self-alignment with all other chips on the substrate. Hence alignment according to this technique is achieved by the precise formation of the pockets and the precise formation of the complimentary edges of the chips.
Therefore, there is a need for a carrier that can mount one or more inkjet printheads in alignment with one another without the need to form precise pockets within the carrier.
Broadly, the present invention is embodied in a common carrier that includes a carrier substrate for adhering a plurality of unprocessed integrateable chips. Once adhered, the carrier substrate is lithographically processed to form integrated chips that are aligned on the carrier substrate is within lithographic alignment tolerances.
In accordance with one embodiment of the common carrier of the present invention and method of forming thereof, a common carrier is formed to include a plurality of integrated chips and a carrier substrate, where the unprocessed integrateable chip form of the integrated chips are first adhered using a first placement alignment tolerence to the carrier substrate and then are lithographically processed to obtain the plurality of integrated chips on the carrier substrate such that the integrated chips are aligned with each other and the substrate with a second alignment tolerance having lithographic processing precision.
In one embodiment the plurality of integrated chips correspond to a plurality of inkjet printhead IC devices.